Field of Invention
The present invention relates to a noise-cancelled capacitive touch display apparatus; particularly, it relates to such a noise-cancelled capacitive touch display apparatus capable of obtaining precise noise information from the display panel and effectively blocking the noise.
Description of Related Art
Please refer to FIGS. 1A and 1B. FIG. 1A shows a top view of a conventional capacitive touch display apparatus. FIG. 1B shows a cross sectional view of the conventional capacitive touch display apparatus taken along line X-X′ of FIG. 1A. The conventional capacitive touch display apparatus 10 shown in FIG. 1B can be, for example, a mutual capacitance type touch panel. The capacitive touch display apparatus 10 typically comprises a capacitive touch sensor 11 and a display panel 12. The capacitive touch sensor 11 is located on or above the display panel 12; therefore, only the capacitive touch sensor 11 of the conventional capacitive touch display apparatus 10 is shown in the top view of FIG. 1A, because the display panel 12 is located below the capacitive touch sensor 11 (as shown in FIG. 1B) and can not be seen from the top view of FIG. 1A. The display panel 12 can be, for example but not limited to, a liquid crystal display (LCD) panel or an organic light emitting diode (OLED) panel.
The capacitive touch sensor 11 includes plural driving lines DA1˜DA9 in columns and plural sensing lines SA1˜SA9 in rows. The driving lines DA1˜DA9 and the sensing lines SA1˜SA9 are located at different layers. The driving lines DA1˜DA9 and the sensing lines SA1˜SA9 intersect with each other (i.e., each driving line DA1˜DA9 intersects every sensing line SA1˜SA9 and each sensing line SA1˜SA9 intersects every driving line DA1˜DA9) so as to form an electric field. For better sensing effect, preferably, the driving lines DA1˜DA9 and the sensing lines SA1˜SA9 can be arranged orthogonal to each other. As shown by the top view of FIG. 1A, the intersections where the driving lines DA1˜DA9 and the sensing lines SA1˜SA9 overlap with each other are the sensing nodes N11, N12, N13 . . . , N98, and N99. The capacitive touch sensor 11 can adopt, for example but not limited to, a so-called mutual capacitive type sensing method to sense the touched locations. The so-called mutual capacitive type sensing method is to monitor the capacitance change at each of the sensing nodes N11, N12, N13 . . . , N98, and N99 in the capacitive touch sensor 11 of the conventional capacitive touch display apparatus 10. For example, assuming that the capacitive touch sensor 11 includes J driving lines and K sensing lines, a total of (J×K) individual and spatially separated sensing nodes are thereby formed. In the example shown in FIG. 1A, the capacitive touch sensor 11 includes 9 driving lines DA1˜DA9 and 9 sensing lines SA1˜SA9, thereby forming a total of 81 individual and spatially separated sensing nodes N11, N12, N13 . . . , N98, and N99. During operation, each of the driving lines DA1˜DA9 receives a driving voltage (not shown) and because each of the driving lines DA1˜DA9 intersects every one of the sensing lines SA1˜SA9 at the intersections (i.e., the sensing nodes N11, N12, N13 . . . , N98, and N99), a mutual capacitance is generated at each node, and a corresponding voltage can be sensed at each node. When a location on the display panel 12 is touched, the mutual capacitance of a corresponding sensing node in the capacitive touch sensor 11 changes, and the sensed voltage correspondingly changes. This feature can therefore be used to determine whether and where the display panel 12 is touched.
Still referring to FIG. 1B, as shown in the figure, the capacitive touch sensor 11 further includes a substrate 14. The sensing lines SA1˜SA9 of the capacitive touch sensor 11 can be formed at one side 141 of the substrate 14 and the driving lines DA1˜DA9 of the capacitive touch sensor 11 can be formed at an opposite side 142 of the substrate 14. In such configuration, the driving lines DA1˜DA9 and the sensing lines SA1˜SA9 do not directly contact each other; instead, the driving lines DA1˜DA9 and the sensing lines SA1˜SA9 are capacitively coupled to each other at the intersections (N11, N12, . . . , N98, N99) with the substrate 14 in between. For example, an overlapping intersection of a driving line (e.g., DA9) and a sensing line (e.g., SA9) forms a sensing node (e.g., N99) as shown in FIG. 1A and FIG. 1B. Such an intersection (i.e., a sensing node) is a position where one of the driving lines DA1˜DA9 and one of the sensing lines SA1˜SA9 cross or come nearest to each other from top view, but they are in fact at different elevation planes from cross sectional view.
In the capacitive touch sensor 11, for example, the driving line DA9 and the sensing line SA9 are capacitively coupled to each other at the sensing node N99 to generate a mutual capacitance. That is, because the voltage level of the driving line DA9 is different from that of the sensing line SA9, magnetic field lines are formed at the sensing node N99 (as shown in FIG. 1B). FIG. 2 shows an explosion view of FIG. 1B. Generally, in such a configuration wherein the capacitive touch display apparatus 10 is formed by combining the display panel 12 with the capacitive touch sensor 11, the noises generated from the display panel 12 will interfere with the capacitive touch sensor 11. FIG. 2 explains how the noises generated from the display panel 12 interfere with the capacitive touch sensor 11. As compared to a single-layer type capacitive touch sensor 11 (i.e., a capacitive touch sensor whose driving lines and sensing lines are arranged on the same side of a substrate), the two-layers type capacitive touch sensor 11 as shown in FIG. 1B and FIG. 2 can make use of the driving lines DA1˜DA9 to block the noises generated from the display panel 12 so that they do not interfere with the capacitive touch sensor 11 (e.g., as shown in FIG. 2, the noise A coming from beneath the driving line DA1 is blocked, so that the noise A will not be capacitively coupled to the sensing line SA9 and therefore there will be no mutual capacitance generated by the noise A coupling with the sensing line SA9).
However, there are gaps between two neighboring driving lines (e.g., between driving lines DA1 and DA2 or driving lines DA8 and DA9), so the noise B generated from the display panel 12 can still be capacitively coupled to the sensing lines (e.g., the sensing line SA9) of the capacitive touch sensor 11 to generate a mutual capacitance by the noise B coupling with the sensing line SA9 (e.g., as shown in FIG. 2, the noise B can pass through the gap between driving lines DA1 and DA2 or the gap between driving lines DA8 and DA9). Thus, the capacitive touch sensor 11 is still affected by the noise B, and the conventional capacitive touch display apparatus 10 can not completely block the noises generated from the display panel 12 to prevent such noises from interfering with the capacitive touch sensor 11.
To overcome the drawback mentioned in the above-mentioned prior art, another prior art proposes to add a grounded shielding layer between the display panel and the capacitive touch sensor, for blocking the noise generated from the display panel. However, such an arrangement not only increases the manufacturing cost but also affects the display performance of the display panel.
Besides the above-mentioned prior art, the following patents and publications are relevant to the present invention: U.S. Pat. Nos. 8,493,356; 8,497,844; US 20060103635; US 20110242045; US 20120001859; US20120306803; US20120326992; US20130057337; US20130069904; US20130147755; US20130169585; US20130176233 and US20130222290. Nevertheless, these prior art references all fail to overcome the drawback mentioned in the above-mentioned prior art of FIGS. 1A-1B and FIG. 2.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a noise-cancelled capacitive touch display apparatus capable of obtaining precise noise information from the display panel and effectively blocking the noise.